A volume of fluid, such as air, can be characterized by a temperature and pressure. When considered as a collection of constituent particles, comprising, for example, molecules of oxygen and nitrogen, the volume of fluid at a given temperature can be understood as a distribution of constituent particle speeds. This distribution can be characterized, generally, by an average speed which can bear a relationship with the temperature of the gas.
The internal atomic and molecular structure of constituent particles, which can provide a range of accessible internal energy states, can also affect the temperature distribution of the gas. The range of accessible internal energy states associated with an atom or molecule, in turn, can be affected by the geometry and properties of its surroundings.